Optical system for effecting increased irradiance in peripheral area of object.

摘要

Disclosed is a novel optical system for illuminating an object with effecting an increased irradiance in the peripheral area of the object. The optical system includes a light source, an entrance pupil for receiving light from the light source, an exit pupil for passing the light received to the object, and an optical axis which extends to the light source and the object, respectively, through the optical system, wherein the relationship among the incident height h to the entrance pupil, an illumination height H on the object and a changing rate (dh/dH) of the incident height and the illumination height is defined by a function, f(H)=(h/H)(dh/dH). The optical system is designed so as to satisfy the following formula in the peripheral area of the object: f(0)<f(H). The function f(0) is represented by: f(0)=[fa min /{(a min -f)b min }]<2>, where a min is a distance between the light source and the primary principal point of the optical system, and b min is a distance between the real image of the light source and the object.